io.permazen

Class SnapshotJTransaction

java.lang.Object

io.permazen.JTransaction

io.permazen.SnapshotJTransaction

All Implemented Interfaces:

Closeable, AutoCloseable

public class SnapshotJTransaction
extends JTransaction
implements Closeable

A "snapshot" JTransaction that persists indefinitely.

SnapshotJTransactions hold a "snapshot" some portion of the state of a JTransaction for later use. Each SnapshotJTransaction contains its own set of "snapshot" JObjects that are (usually) copies of the corresponding "real" database JObjects. Because a SnapshotJTransaction lives indefinitely, these objects can be used just like normal Java objects, outside of any regular transaction. In addition, Permazen features such as indexing, listeners, validation, etc. also continue to work normally.

For convenience, each JTransaction has a default SnapshotJTransaction instance associated with it; JObject.copyOut() copies objects there.

More general usage is possible via JTransaction.createSnapshotTransaction(). For example, for KVDatabases that support it, using the key/value store snapshot returned by KVTransaction.mutableSnapshot() allows an efficient copying of the entire database.

See Also:

Transaction.createSnapshotTransaction(), Permazen.createSnapshotTransaction(), SnapshotTransaction

Method Summary

Modifier and Type	Method and Description
void	close() Close this instance and release any resources associated with it.
void	commit() Commit this transaction.
SnapshotTransaction	getTransaction() Get the SnapshotTransaction associated with this instance.
boolean	isSnapshot() Determine whether this instance is a SnapshotJTransaction.
boolean	isValid() Determine whether this transaction is still valid.
void	reset() Delete all objects contained in this snapshot transaction and reset it back to its initial state.
void	rollback() Roll back this transaction.

Methods inherited from class io.permazen.JTransaction

cascadeFindAll, cascadeFindAll, copyTo, copyTo, copyTo, copyTo, create, create, createClones, createSnapshotTransaction, delete, exists, followReferencePath, get, get, get, getAll, getCurrent, getKey, getKey, getPermazen, getSchemaVersion, getSnapshotTransaction, getValidationMode, invertReferencePath, performAction, queryCompositeIndex, queryCompositeIndex, queryCompositeIndex, queryIndex, queryIndex, queryListElementIndex, queryMapValueIndex, queryVersion, readCounterField, readListField, readMapField, readSetField, readSimpleField, recreate, registerJObject, resetValidationQueue, revalidate, setCurrent, updateSchemaVersion, validate, weakConsistency, writeSimpleField

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

isSnapshot

public boolean isSnapshot()

Description copied from class: JTransaction

Determine whether this instance is a SnapshotJTransaction.

Overrides:

isSnapshot in class JTransaction

Returns:

true if this instance is a SnapshotJTransaction, otherwise false

getTransaction

public SnapshotTransaction getTransaction()

Get the SnapshotTransaction associated with this instance.

Overrides:

getTransaction in class JTransaction

Returns:

the associated core API snapshot transaction

reset

public void reset()

Delete all objects contained in this snapshot transaction and reset it back to its initial state.

It will contain schema meta-data but no objects.

commit

public void commit()

Commit this transaction.

SnapshotJTransactions do not support this method and will always throw UnsupportedOperationException.

Overrides:

commit in class JTransaction

Throws:

UnsupportedOperationException - always

rollback

public void rollback()

Roll back this transaction.

SnapshotJTransactions do not support this method and will always throw UnsupportedOperationException.

Overrides:

rollback in class JTransaction

Throws:

UnsupportedOperationException - always

isValid

public boolean isValid()

Determine whether this transaction is still valid.

SnapshotJTransactions are always valid.

Overrides:

isValid in class JTransaction

Returns:

true always

See Also:

Transaction.isValid()

close

public void close()

Close this instance and release any resources associated with it.

The implementation in SnapshotJTransactions closes the underlying SnapshotTransaction.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

See Also:

SnapshotTransaction.close()